Adsorbent masses for CO.sub.2 have been known, which are used to bind the exhaled CO.sub.2 in recirculating respirators. Such adsorbent masses are often referred to as respirator lime. Respirator lime adsorbent consists essentially of calcium hydroxide containing a certain percentage, usually 14-18% of water. To increase the reactivity, the prior-art respirator lime adsorbent usually contains a few percent sodium hydroxide or potassium hydroxide. For use in respirators, the respirator lime adsorbent must be granulated The particle size of the granules ranges from 2 mm to 8 mm, depending on the intended use. Crushed granules or shaped lime particles with a diameter of about 4 mm are used very frequently. The prior-art types of respirator lime adsorbents have generally good CO.sub.2 binding properties However, if they are used in personal respirators exposed to high mechanical stresses, e.g., in an oxygen-supplying escape apparatus, they are destroyed in a short time due to the lack of strength to the point that the respirators generate much dust and their fitness for use is no longer guaranteed. The use of the prior-art types of respirator lime adsorbents in oxygen-supplying escape apparatus is therefore associated with a great risk.
Attempts to increase the strength of respirator adsorbent lime have been reported on numerous occasions, but they always led to a marked reduction of reactivity. These attempts include, for example, the use of alkali silicates as an additive to the calcium hydroxide paste. Liquid alkali silicates (water glass) cause strengthening of the structure of the calcium hydroxide granules, but they reduce its porosity and form an outer layer of greatly reduced reactivity on the lime granule. This makes it necessary to use more respirator adsorbent lime to maintain a sufficient CO.sub.2 adsorption capacity, as a result of which the respirators become bulkier, heavier, and clumsier. This is highly undesirable, especially in the case of an escape apparatus.